CN112228905A

CN112228905A - Channel structure capable of restraining flow distribution deviation of supercritical fluid

Info

Publication number: CN112228905A
Application number: CN202011089489.6A
Authority: CN
Inventors: 姜俞光; 周启林; 王常伟; 张晋; 范玮
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2020-10-13
Filing date: 2020-10-13
Publication date: 2021-01-15
Anticipated expiration: 2040-10-13
Also published as: CN112228905B

Abstract

The invention provides a channel structure capable of inhibiting flow distribution deviation of a supercritical fluid, which comprises a refrigerant inlet, an inlet liquid collecting cavity, a liquid cavity, a mixing cavity, a supercritical state cavity, an outlet liquid collecting cavity and a refrigerant outlet, wherein the liquid cavity comprises a plurality of uniform-section flow channels which are arranged in parallel, the mixing cavity comprises a plurality of wedge-shaped turbulent flow structures which are regularly arranged, and the supercritical state cavity comprises a plurality of variable-section flow channels which are arranged at equal intervals. The channel structure can enable fluids near critical states among the flow channels to be mixed with each other, so that pressure difference and temperature difference among the flow channels are reduced, the sensitivity of flow resistance of the supercritical fluid to wall surface heat flow change can be reduced, flow distribution deviation among the flow channels in a multi-mode thermal environment is restrained, and flow distribution uniformity is improved.

Description

Channel structure capable of restraining flow distribution deviation of supercritical fluid

Technical Field

The invention belongs to the technical field of flow and heat transfer, and particularly relates to a channel structure capable of inhibiting flow distribution deviation of a supercritical fluid.

Background

The hypersonic aircraft using the scramjet engine as power is a research hotspot which is extremely concerned by various military and strong countries. Compared with other engines, the scramjet engine has the advantages of relatively simple structure, low cost and long range, and can form a combined engine with other engines to enlarge the flight range, such as TBCC and RBCC, so that the scramjet engine is considered as an ideal power source for realizing hypersonic flight in the atmosphere.

With the increase of the flight Mach number, the scramjet engine faces very severe thermal environment tests. When the incoming flow Mach number is 6, the stagnation temperature can reach 1600K, the temperature of the burnt gas exceeds 2700K, and the maximum value of the wall surface heat flux density reaches 10-20MW/m². If only the passive material is relied on, the safe operation of the engine under the conditions of long endurance and high Mach number cannot be ensured. Regenerative cooling, in which the carried hydrocarbon fuel is selected as the coolant, is a mainly adopted active thermal protection method. Specifically, in the technical implementation of regenerative cooling, the cooling channels are arranged on each heat flow wall surface in parallel, and the flow direction is parallel to the whole axial direction of the engine. In the actual working process, the flow of each branch of the parallel channel system inevitably has cold state deviation due to inherent properties such as branch and confluence. Under the heating condition, the hydrocarbon fuel absorbs heat from the liquid state and enters the supercritical state, the physical properties are changed violently, the flow resistance among all branches is changed, and in order to match the pressure drop relation of an inlet and an outlet, the flow of all branches is redistributed in a self-adaptive manner. For example, under the same heating condition, the temperature rise of the minor flow branch in the cold state deviation is fast, the density is low, the flow velocity of the fluid in the branch is increased, the resistance is increased, so the resistance can be reduced only by reducing the flow, the condition that the pressure difference at the two ends of each parallel channel is equal is met, and the flow distribution deviation among the branches is aggravated by wall surface heating. In addition, the combustion heat release and the pneumatic heating apply an unsteady, non-uniform thermal load to the wall, i.e., the wall heat flow is a time-varying, distributed parameter, which leads to further aggravation of the flow deviation between the branches. Therefore, unreasonable utilization of fuel cooling capacity, serious waste of limited heat sink and even terrible burning of the engine due to overhigh local wall temperature can occur.

In order to meet the cooling requirement, the flow deviation among all branches needs to be controlled, the cooling capacity is reasonably distributed, areas with large heat flows are provided, and the flow of the coolant is relatively large. It is not practical to actively control the flow rate of each cooling channel individually to eliminate the flow rate deviation, limited by the structure and the number of cooling channels. The key to solve the problem is to develop a simple and feasible channel structure to effectively restrain the flow deviation among the branches of the complex and changeable heat load.

Disclosure of Invention

Technical problem to be solved

The invention provides a channel structure capable of restraining flow distribution deviation of a supercritical fluid, which is used for reducing flow distribution deviation among cooling channel branches in a multi-mode thermal environment, reasonably distributing cooling capacity, fully utilizing a limited heat sink and avoiding cooling failure caused by local high temperature.

The technical scheme of the invention is as follows:

a channel structure capable of inhibiting flow distribution deviation of supercritical fluid comprises a refrigerant inlet, an inlet liquid collecting cavity, a liquid cavity, a mixing cavity, a supercritical state cavity, an outlet liquid collecting cavity and a refrigerant outlet, wherein the liquid cavity comprises a plurality of uniform cross-section flow channels which are arranged in parallel, the mixing cavity comprises a plurality of wedge-shaped turbulence structures which are regularly arranged, the supercritical state cavity comprises a plurality of variable cross-section flow channels which are arranged at equal intervals, and the number and the positions of the uniform cross-section flow channels correspond to those of the variable cross-section flow channels respectively.

Furthermore, the center of the mixing cavity is arranged at the critical state fluid of the high-temperature runner of the traditional channel structure, the flow direction length of the mixing cavity is larger than 10 times of the runner width of the liquid cavity, and the traditional channel structure is a channel structure with the whole inner runner designed by the structure of the inner runner of the liquid cavity.

Furthermore, the wedge-shaped turbulence structures and the liquid cavity runner are arranged in a staggered mode at intervals, and the width of each wedge-shaped turbulence structure is equal to that of the liquid cavity runner.

Further, the area ratio of the inlet-outlet cross sections in the variable cross-section flow passage is more than 0.5 and less than 1.

Advantageous effects

According to the channel structure capable of inhibiting the flow distribution deviation of the supercritical fluid, fluids near the critical state among the flow channels can be mixed with each other through the mixing chamber, so that the pressure difference and the temperature difference among the flow channels are reduced; the flow velocity of the supercritical fluid can be reduced through the supercritical chamber variable cross-section flow channel, so that the sensitivity of the flow resistance to the change of wall surface heat flow is reduced, the flow distribution deviation among parallel channels under the action of non-uniform and unsteady heat load is reduced, the cooling capacity is reasonably distributed, the temperature distribution of a cooling area is more uniform, and the component failure caused by heat stress is avoided.

Drawings

FIG. 1 is a semi-sectional isometric view of a channel structure for suppressing the flow distribution deviation of supercritical fluid;

FIG. 2 is a schematic view of the internal flow passages of a channel structure for suppressing the flow distribution deviation of a supercritical fluid;

fig. 3 is a schematic view of an internal flow passage of the conventional channel structure.

In the figure, 1 is a refrigerant inlet, 2 is an inlet liquid collecting cavity, 3 is a liquid cavity, 4 is an equal-section flow channel, 5 is a mixing cavity, 6 is a wedge-shaped turbulence structure, 7 is a supercritical state cavity, 8 is a variable-section flow channel, 9 is an outlet liquid collecting cavity, and 10 is a refrigerant outlet.

Detailed Description

The present invention will be described in further detail below with reference to the accompanying drawings.

The invention relates to a channel structure capable of restraining flow distribution deviation of a supercritical fluid, which is an I-shaped cooling channel with a vertical inlet in the embodiment. As shown in fig. 1 and 2, it includes: the device comprises a refrigerant inlet 1, an inlet liquid collecting cavity 2, a liquid cavity 3, an equal-section flow channel 4, a mixing cavity 5, a wedge-shaped turbulent flow structure 6, a supercritical state cavity 7, a variable-section flow channel 8, an outlet liquid collecting cavity 9 and a refrigerant outlet 10. The liquid cavity 3 is provided with a plurality of uniform cross-section flow passages 4 in parallel, the mixing cavity 5 is regularly provided with a plurality of wedge-shaped turbulence structures 6, the supercritical cavity 7 is provided with a plurality of variable cross-section flow passages 8 at equal intervals, the number and the positions of the uniform cross-section flow passages 4 correspond to the variable cross-section flow passages 8 respectively, and the width and the number of the uniform cross-section flow passages 4 are determined according to actual working conditions. The flow direction length of the mixing cavity 5 is larger than 10 times of the width of the uniform cross-section flow channel 4, the wedge-shaped turbulence structures 6 are arranged at intervals in a staggered mode with the same cross-section flow channel 4, the width of each wedge-shaped turbulence structure 6 is equal to the width of the uniform cross-section flow channel 4, the length of each wedge-shaped turbulence structure 6 is determined jointly according to the working condition thermal environment and the flow direction length of the mixing cavity 5, the area ratio of the inlet cross section to the outlet cross section in the variable cross-section flow channel 8 is larger than 0.5 and smaller than 1, and therefore the phenomenon.

The center position of the mixing chamber 5 is arranged at the critical-state fluid of the high-temperature flow channel of the traditional channel structure (figure 3), and the position of the critical-state fluid of the high-temperature flow channel is determined by three-dimensional numerical simulation of Fluent under a given thermal environment.

Working process

The cooling process of the present invention is described below with a hydrocarbon fuel as the refrigerant, with the inlet in liquid form and the outlet in supercritical form, providing a non-uniform lower wall heat flow that gradually decreases in the width (y) direction. The comparison between the comparative example and the example in the invention is used for verification.

Comparative example: the traditional channel structure (figure 3) is adopted, and different from the cooling structure in the invention, the whole inner flow channels are designed by adopting the inner flow channel structure of the liquid cavity 3, and the wedge-shaped turbulence structure 6 and the variable cross-section flow channel 8 are avoided.

Example (b): by adopting the cooling channel structure, other boundary conditions such as refrigerant flow, wall surface heat flow and the like are consistent with those of the comparative example.

The cooling procedure for the comparative example is as follows: due to the inherent property of shunting, the branch A far away from the refrigerant inlet 1 inevitably obtains the minimum refrigerant flow, and at the moment, the branch A corresponds to the highest wall surface heat flow load, the temperature rise of fluid in the branch A is fast, the density is low, the fluid flow speed is high, and the flow resistance is increased, so the branch A can only reduce the resistance by reducing the flow until the condition that the pressure difference at two ends of each parallel channel is equal is met, the flow of the branch A bearing the highest heat load is further obviously reduced, the cooling capacity at the position of the highest heat load is seriously insufficient, and local high temperature is generated, and even the wall surface of the channel is burnt.

The cooling process of the example is as follows: firstly, the fluid entering into the supercritical state has low density, high flow speed and large flow resistance, the fluid flow resistance of the branch A in the comparative example mainly exists in the rear supercritical fluid section, and the fluid flow resistance of the front liquid fluid section is smaller. And in other branches with higher flow in the comparative example, the viscosity of the liquid fluid at the front section is higher at the same flow direction length, the flow velocity is high, the flow resistance is higher than that of the branch A, and the pressure of the critical fluid of the branch A in the comparative example is obviously higher than that of other branches with the same flow direction length because the inlet and outlet pressures of all the parallel branches are equal. Meanwhile, the temperature of each branch also has larger deviation due to the flow deviation of the branch. In the embodiment, the mixing chamber 5 with a certain length is arranged at the critical state fluid of the branch A in the comparative example, and the wedge-shaped turbulence structures 6 are arranged in the same cross-section flow channel 4 at intervals in a staggered manner, so that the mixing among the fluids of the branches is realized, the pressure and the temperature of the branch A are reduced, and the flow of the branch A is increased. In addition, aiming at the low density, high flow speed and large flow resistance of the supercritical fluid, in the embodiment, the variable cross-section flow channel 8 is adopted for the flow of the supercritical fluid at the rear section, so that the increase of the flow speed is inhibited, the sensitivity of the flow resistance of the internal fluid to the change of the wall surface heat load is obviously reduced, the flow reduction of the branch circuits A under high heat flow is inhibited to a certain extent, and the flow distribution uniformity among the branch circuits is improved.

Claims

1. A channel structure capable of suppressing flow distribution deviation of a supercritical fluid, characterized in that: the device comprises a refrigerant inlet, an inlet liquid collecting cavity, a liquid cavity, a mixing cavity, a supercritical cavity, an outlet liquid collecting cavity and a refrigerant outlet, wherein the liquid cavity comprises a plurality of uniform-section flow channels which are arranged in parallel, the mixing cavity comprises a plurality of regularly arranged wedge-shaped turbulence structures, the supercritical cavity comprises a plurality of variable-section flow channels which are arranged at equal intervals, and the number and the positions of the uniform-section flow channels correspond to the variable-section flow channels respectively;

the center of the mixing cavity is arranged at the critical state fluid of the high-temperature runner of the traditional channel structure, the flow direction length of the mixing cavity is more than 10 times of the runner width of the liquid cavity, and the traditional channel structure is a channel structure with the whole inner runners designed by the structure of the inner runners of the liquid cavity;

the wedge-shaped turbulence structures and the liquid cavity runner are arranged at intervals in a staggered mode, and the width of each wedge-shaped turbulence structure is equal to that of the liquid cavity runner;

the area ratio of the inlet and outlet cross sections in the variable cross-section flow channel is more than 0.5 and less than 1.